Means for testing the potency of a microorganism inhibitor



y 1949- J. F. NORTON 2,476,899

MEANS FOR TESTING THE POTENCY 0F MICROORGANISM INHIBITORS Filed Nov. 17, 1945 2 Sheets-Sheet 1 INVENTOR JOHN FNURT N I 0 BY /7/ L .l

- ATTORNEY y 1949. J. F. NORTON 2,476,399

MEANS FOR TESTING THE POTENCY OF MICROORGANISM INHIBITORS Filed Nov. 17, 1945 2 Sheets-Sheet 2 F mn .m- III] INVENTOR JOHN F NORT N Patented July 19, 1949 MEANS FOR TESTING THE POTENCY OF A MICROORGANISM INIHBITOR John F. Norton, Kalamazoo, Mich., assignor to .The Upjohn Company, Kalamazoo, Mich., a

corporation of Michigan Application November 17, 1945, Serial No. 629,239.

4 Claims.

This invention relates to a means for making a germicidal, antiseptic or antibiotic assay, and

particularly contemplates a measuring means which will provide an optical analysis of results which may be directly interpreted on a scale. 5 vention is to provide a means for measuring In a standard method for determining the the area of a culture-free, or culture inhibited, strength of a sample of germicidal, antiseptic or portion of an otherwise cultured medium which antibiotic substance, a culture is developed in a can be operated rapidly, which substantially resuitable medium to a desired concentration and duces from present methods the judgment reat a selected point in such development a prequired of the individual operator and which determined quantity of the substance being asmeans can be readily calibrated to read in whatsayed is placed at a selected part of the cultured ever units are desired. medium. After a given length of time the sub- A further object of my invention is to provide stance will have destroyed, or substantially inan instrument which will be simple and economihibited the growth of, the bacteria, or other culcal to construct. ture substance, for a distance radially from the A further object of my invention is to provide point of application which is a function of the .an instrument for which the manner of operation germicidal, antiseptic or antibiotic strength of can be readily learned. the said substance. Hence, measurement of the A fu t er O ject Of y invention s Provide area of the cultured medium in which the culn in m n as aforesaid which will be comture has been destroyed, or'its growth inhibited, posed of simple and relatively sturdy parts so in a selected length of time will provide a measthat it will withstand normal usage over a long urement of the strength of the said substance. period of time without getting Out Of a j en Reference is made to the Federal Register of O her object and p rposes of my invention will September 8, 1945, for further particulars relatbe pp to those acquaintd w h his type ing tothis method of assay as applied especially of equipment upon examination of the accomto penicillin. The general process has been known pa y drawings and reading of the following for many years as applied to germicidal and antidisclosure. septic substances broadly. In the drawings:

In carrying out this method, the step of meas- Figure 1 is a side elevation view of an instruuring the area of the culture free portion of meri e ody y invention and by which the cultured medium has been rather time-cony measuring method y be p t ced. suming and not always sufliciently accurate. F gure 2 is a top view of said instrument. I Where diameters are measured directly and, as Figure 3 is a ear v ew of said instrument. frequently happens, the culture free area is not Figure 4 is a section taken on the line IV--IV exactly circular, it requires a substantial expendiof Figure 2 looking in the direction of the arrows. ture of time to measure with ordinary measuring In developing an instrument meeting the obinstrume'nts a sufficient number of diameters to jectives and purposes above stated, I have utilized determine an average diameter and to insure the fact that the culture free, or culture inreasonable accuracy. Further, even with such 40 hibited, area of the medium possesses a greater expenditure of time in measuring a number of degree of light transmissiveness than the fully different diameters, the judgment of the operator cultured area. Thus, by placing the culture must still be depended upon to determine whether medium in a transparent or at least translucent, the proper diameters have been measured, unless dish and illuminating same from one side thereof the number of diameters actually measured has 5 it is necessary only to examine the medium from been very great. Where a grid is superimposed the side opposite the light source and determine over the culture free, or culture inhibited, area the area of the light transmitting portion. This the counting of lines is laborious and of somelatter step I have accomplished by arranging a times questionable accuracy. Therefore, it is desuitable optical system together with an iris. The sirable to provide an instrument which will make operator looks through the elements of the optithis measurement in a rapid and more accurate cal system and manually adjusts the iris until its manner and which may be calibrated for direct circumference is as nearly as possible coincident reading of either diameter or area, or both, as with the perimeter of the area within the cultured desired. It is further desirable that such an inmedium having the greater light transmitting strument provide visual analysis of the entire capacity. Apointer mechanically associated with area in question so that the operator may immediately observe any irregularities in said area and, easily compensate for them.

Accordingly, the major object of my insaid iris indicates its degree of'opening in terms either of diameter or of area, or both, as desired for any given position.

Looking now at the fi res in more detail there is-provided a box-shaped base member I which is light-tight throughout excepting from an opening 2 in its upper side. This opening iscovered by a frosted glass 3 suitably held adjacent said opening by any convenient means, such as the brackets 4. Within the box there is provided a source of illumination 5 such as an incandescent electric light. This light source will be provided with suitable energizing means and a switch, neither of which are here shown. The base may be supported by suitable frame members 6 which 4 in Figure 4 to reduce the intensity of light reaching the operator's eye. This is not essential to ,the operation or my measuring device but is de- At the lower end of the analyzing portion of my device and below the lens l9, there is located a standard iris 23 having the usual overlapping are here shown as rods for holding the instrument at a convenient working angle with respect to a table A, butwhich may be of any convenient form. l

A platform Lfor holding the medium containing means, such as a Petri dish B, is located directly above the opening 2 and may be supported in any convenient manner. An opening 8 is protically aligned therewith an opening I2 is provided through the bottom part of the said well.

A supporting pin I3 depends from the underside of the platform I through the openings II and I2. A collar I4 is mounted on said pin in any convenient manner, as by pressing thereon, which collar backs a spring l5 resting at its other end against the bottom of the well 9. Thus the platform is resiliently mounted so that the Petri dish B is easily inserted and then held firmly against the hereinafter described members of the analyzing part of the device. It thus provides means of holding the cultured medium C as closely as possible to, but a uniform distance from, the hereinafter mentioned iris,

The analyzing portion of this device is mounted directly above the opening 8 in the platform and is supported by a suitable bracket I G which is mounted on the base I and supports the barrel base I1. This base supports the barrel I8, which conveniently consists of telescoping parts l8a and I8b. Held below the base I! and the supporting frame it; is convex lens I 9 mounted in any convenient manner. At the upper'end of the barrel part 18a is an eye-piece 20 which comprises either an opaque disk with a small opening, therein, or it may include another lens if desired for better magnification. However, for ordinary purposes the one lens I9 is suflicient, so that the eye-piece 20 may usually be formed as shown as an opaque member with a small opening in its center. spectively spaced from the platform a distance such that the surface of the cultured medium C held in the Petri dish B on the platform 1 will be in proper focus to the operator's eye when positioned above but close to said eye-piece. While no adjustable focusing means other than the telescoping barrel I! are here shown, such .may be readily provided in any standard manner if desired. A plurality of suitable light filters 2| and 22 are placed in the line of vision, such as between the lens I 9 and the eye-piece 20 as shown An opening II The lens l9 and eye-piece 20 are replates 24 and a central substantially circular opening 25 of variable size. The iris is operated in any convenient and standard manner by a handle 26 and supports near its end an indicator 21. This indicator travels over a scale 28 which is arranged and calibrated to indicate either the diameter, or the area, or both as desired, of the culture inhibited partof the cultured medium in any given adjusted position of said iris.

The operation of the device is simple. With the light source iilluminated, a specimen such as a transparent or translucent dish 3 containing the cultured medium C to-be examined is placed on the platform 'I and centered with respect to the opening 8 therein. The operator looks through the eye-piece 20 and adjusts the arm 26 in such a manner that the iris opening substantially coincides with the lighter area D of the cultured medium. While "some judgment will be required to determine this coincidence it will be much less than is now required for making direct measurements and will, in fact, be found relatively easy. When the iris is thusad-' justed the diameter and/or area of the culture free portion of the culture medium may then be directly read from the scale 28.-

It should be noted that while the scale may .be made to read in terms of the iris opening and that standards may be set unaccordingly; it will be much preferred to calibrate said scale to read directly in terms of the diameter and/or area of the culture free, or culture inhibited, portion of the'cultured medium in order that the resultsv of assay by this device may be compared with results of assay by conventional methods.

While, as above noted, more lenses than the single one shown may be used, the use of only one lens will be advantageous over the use of two lenses in that it will provide at the eye-piece without special focusing a real image of both the surface being studied and the iris opening, even though said images will be of slightly different degrees of magnification. Thus, even though the iris and said surface are required to be a substantial distance apart, both elements will be sharp and clear as viewed from the eye-piece.

Several variations may be made from the specific structure herein dislcosed which will fall within the scope of my invention and accordingly the hereinafter appended claims should be read to include such variations excepting-as they are excluded by the express terms of said claims.

I claim:

a 1. In apparatus for measuring the diameter of an area of one light transmitting capacity which is surrounded by a medium of a different positioned between said eyepiece and said source of illumination; means for supporting said transparent member between said iris diaphragm and mined distance from said iris diaphragm and with said area concentric with said his diaphragm, whereby light from said source of illumination passes through both said area and said medium to said eyepiece; means operatively connected to said iris diaphragm for adjusting the diameter of its opening and indicating on a scale a predetermined function of the diameter of said opening when the iris diaphragm is adjusted to pass to the eyepiece only light emanating from said area.

2. In apparatus adapted for receivingja specimen having an area of one light transmitting capacity which is surrounded by a medium of a difl'erent light transmitting capacity and for measuring the diameter of said'area, the combination comprising: a frame; a source of illumination of substantially uniform intensity attached to said frame; an iris diaphragm mounted on said frame; means for supporting said specimen between said iris diaphragm and said source of illumination spaced a predetermined distance from said iris diaphragm and with said area co-axial with the opening in said iris diaphragm; an optical system including an eyepiece spaced from said iris diaphragm in a direction opposite from said source of illumination and mounted on said frame in alignment with said iris diaphragm, area and source of illumination for receiving light from said source passing through both said area and said medium; means operatively connected to said iris diaphragm for adjusting the diameter of its opening and indicating on a scale a predetermined function of the diameter of said opening when the iris diaphragm is adjusted to pass to the eyepiece only light emanating from said area.

3. An apparatus for measuring the potency of a given quantity of a micro-organism inhibitor which micro-organism inhibitor is placed upon an inoculated culture plate for creating a zone of inhibition of micro-organic growth of one light transmitting capacity surrounded by an uninhibited culture zone of a different light transmitting capacity, the combination comprising: a supporting frame; a source of illumination and an eyepiece supported by said frame; an iris diaphragm mounted on said frame between said source of illumination and said eyepiece; means for positioning said culture plate between said source of illumination and said iris diaphragm spaced a predetermined distance from said iris diaphragm and with said zone of inhibition of micro-organic growth aligned with said source of illumination, said iris diaphragm and said eyepiece; said source of illumination proiecting light rays of substantially equal intensity through both said zone of inhibition of microorganic growth and said surrounding uninhibited culture zone to said eyepiece; a scale and means operatively connected to said iris diaphragm for adjusting the diameter of its opening and indicating on said scale a predetermined function of the diameter of said opening when the iris diaphragm is adjusted to pass to the eyepiece only light emanating from said zone of inhibition of micro-organic growth.

4. An apparatus for measuring the potency of. a given quantity of growth inhibitor which growth inhibitor is placed upon an inoculated culture plate for creating an area of inhibition of growth of one light transmitting capacity surrounded by a zone of uninhibited growth of a different light transmitting capacity, the combination comprising: a housing having an opening in one end thereof; a source of illumination of substantially uniform intensity mounted within said housing co-axlally with said opening; a frame mounted to said housing; an optical system mounted on said frame co-axially with said opening; an iris diaphragm mounted on said frame between said optical system and said opening and co-axially with said opening and said optical system; means connected with said housing for positioning said culture plate spaced a predetermined distance from said iris diaphragm and with said area of inhibition of growth positioned coaxially with said opening, iris diaphragm and optical system; a-scale and an indicator hand operatively connected to said iris diaphragm for adjusting the diameter of the opening in said iris diaphragm and indicating on said scale a predetermined function of the diameter of said iris diaphragm opening when the iris diaphragm is adjusted to pass to the eyepiece only light emanating from said area of inhibited growth.

JOHN F. NORTON.

REFERENCES crrsn The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,353,151 Deming Sept. 21, 1920 FOREIGN PATENTS Number Country Date 721 Great Britain Jan. 16, 1915 171,054 Switzerland.------ Oct. 16, 1934 

